Air-burst fuze system for projectiles



March 25, 1969 J. BROTHERS AIR-BURST FUZE SYSTEM FOR PROJECTILES FiledJune 26, 1967 INVENTOR. Jack Brothers BY fi W 1.

nrromvsrs United States Patent 3,434,423 AIR-BURST FUZE SYSTEM FORPROJECTILES Jack Brothers, Succasunna, N.J., assignor to the UnitedStates of America as represented by the Secretary of the Army Filed June26, 1967, Ser. No. 650,155 Int. Cl. F42c 13/00 U.S. Cl. 102--70.2 3Claims ABSTRACT OF THE DISCLOSURE The present invention relates to astand-off control or fuze system for functioning an explosive or armedspace vehicle, such as a projectile, a predetermined distance from anobjective or target area. Various fuze systems of this type have beenproposed in the past.

It is an object of this invention to provide an improved system forfunctioning a projectile in the air prior to contact with a target.

It is a further object of this invention to provide an improvedair-burst fuze system wherein functioning occurs when a pre-selectedangle of traverse of the projectile with respect to the firing angle hasbeen met. As the projectile follows its trajectory it traverses an anglewith respect to a gyroscope in the fuze which maintains a fixed attitudewith respect to the original direction or firing angle.

It is also an object of this invention to provide an improved standofior airburst control system of the type referred to, which includessimple means for selectively functioning the projectile for airburst atany desired time or flight angle.

Military and like requirements in this field have presented problems inthe past which have been solved by the use of mechanical, electrical andpyrotechnic time fuzes and by proximity fiizes operated by radiosignals.

These older ways are and have been costly, inaccurate or unreliable inmany instances and subject to being defeated by counter-measures.

In accordance with the system of the present invention an air burst cannow be provided accurately, reliably and inexpensively. The time offlight is no limiting factor. Theoretically the projectile can be flyingfor an indefinite period before the selected traverse angle need be met.

No clock work is required and the number of components is greatlyreduced. The device cannot be defeated by counter-measures, as a radiosignal fuze can be defeated, it does not require the use of pyrotechnicpowders, and it can be hermetically sealed to provide a long shelf life.

Further in accordance with the invention, the explosion initiating trainof the projectile includes an electric detonator which receives firingcurrent through a ground series firing circuit in which are provided anelectrical energy source or pack, a tiggering diode device, gyroscopeand manually adjustable rheostat control elements and an arming switchor like safety device.

A fuze body is provided as a housing for the fuze system and maycomprise the forward or nose cone end of the projectile. A gyroscopeflywheel is pivotally mounted in an inner ring-element which, inv turn,is pivoted in an outer ring element at right angle to its pivot axis.The axis of the gyroscope and the pivot axis of the outer ring elementare aligned with the spin axis of the projectile at the time oflaunching. The gyroscope flywheel and the inner ring unlock from theouter ring on launching and the relative movement controls the gyroscoperheostat to vary the impedance of the firing circuit as the gyroscopeflywheel maintains attitude at takeoff with respect to earth duringflight.

Thus as the angle of the gyroscope flywheel diverges from the spin axisof the projectile in flight, the resistance or impedance of the firingcircuit is reduced and the voltage drop across the triggering diodeincreases until it closes to deliver the full firing current to thedetonator, thus initiating the explosive train of the projectile. Byadjusting the initial impedance or resistances by the manual settingrheostat to different values, the projectile may be set to function atdifferent points along the trajectory, effectively providing selectableair burst therealong.

The invention will further be understood from the following descriptionof a present preferred embodiment thereof, when considered withreference to the accompanying drawings, and its scope is pointed out inthe appended claims.

In the drawings, FIGS. 1 and 2 are plan views, partly in section, of thenose cone of a projectile provided with an air-burst fuze system inaccordance with the invention, the two figures being taken at rightangles one with respect to the other,

FIG. 3 is an enlarged view of a portion of FIG. 2 showing theoperaitonal relation of certain elements thereof, further in accordancewith the invention, and

FIG. 4 is a schematic circuit diagram of a firing cir cuit for thesystem showing certain elements of the preceding figures therein, foroperation in accordance with the invention.

Referring to the drawings, in which like elements in the four figuresare designated by like reference numerals, and referring particularly toFIGS. 1 and 2, the body or housing for the fuze system is the forwardend or nose cone 10 of a space vehicle, such as an explosive projectilein the present example. The fuze housing is thus tapered longitudinallyand provided with interior means for mounting the various elements inpredetermined relation.

These elements include a gyroscope mechanism fixed in the fuze housingor nose cone, and comprising an outer pivot ring or ring element 14, aninner pivot ring or ring element 15, and an inner gyroscope flywheel 16,mounted on pivot axes yy, xx and zz, respectively. The axis of the nosecone or housing 10, that is, the spin or longitudinal axis of theprojectile, is the same as the y-y axis of the outer ring which thusrotates in coaxial relation to the nose cone and the projectile.

As vie-wed in FIG. 1 it will be seen that the outer ring 14 and theinner ring 15 lie in the same plane, with the outer ring pivoted to moveon the axis yy which is in alignment at all times with the direction offlight or longitudinal axis of the projectile. The inner ring 15 ispivoted on the x-x axis in the outer ring 14 at a right angle to the yyand z-z axis. The inner ring thus can move on the axis x-x with respectto the outer ring which must follow the direction of flight of thecarrier 10 on the axis The outer ring 14 is the outer support member ofthe gyroscope. It is connected with the nose cone of housing 10 bylongitudinally-spaced front and rear (or upper and lower) brackets 11and 11A between which it is pivoted on the longitudinal or yy axis ofthe housing or nose cone and which extend across the interior of thenose cone and are secured to the inner wall thereof as indicated in FIG.2. Any other suitable mounting means for the gyroscope elements whichare firmly connected with the housing and provide pivot bearings for theouter ring, as described, may be used.

In coaxial relation to the axis x-x is an annular mounting ring 17Acarrying a semi-circular variable resistor or rheostat element 17 on itsinner face in the plane of movement of the inner ring. The ring orcarrier 17A for the resistor element 17 is connected with and affixed tothe outer ring 14 at a right angle thereto through the axis y-y and iscoaxial with the inner ring 15 on the common axis x-x. The inner andouter rings 15 and 14 are pivoted on axes which are 90 displaced onefrom the other. The carrier or projectile can spin around the axis yywhile the outer ring 14 being pivoted on the same axis may remainstationary with respect thereto.

Both the outer and the inner rings are pivoted at the top and bottom,but are displaced 90 from one another. The outer pivot ring can rotateon its pivots around the axis y-y of the fuze. The fuze body or housing10 provides bearing points for the pivots of the outer pivot ring asabove noted. The outer pivot ring provides bearing points for the innerring 15. An orienting mass (not shown) may be provided on the outer ringto maintain the axis around which the inner ring pivots in a planetangent to the earths surface when the projectile is fired from thelauncher. The outer pivot ring also provides the gyroscope rheostat 17(variable resistance) surface required by the device. The pivots alsoprovide the part of the circuit required.

Referring to FIG. 3, the inner pivot ring 15 is the inner support memberwhich pivots inside the outer pivot ring 14. It provides bearing pointsfor the gyroscope flywheel 16 and it also provides part of the circuitrequired. It provides the gyroscope contact 18 which rides along theresistor element 17 as the relative positions of axes y-y and zztraverse the are or angle y-z. Magnetic attraction or other biasingforce between segments of 15 or 16 and 14 maintains axes y-y and z-z inline until the projectile is fired. Firing removes the magneticattraction and permits traverse of the gyroscope flywheel 16 withrespect to the outer pivot ring 14, as above described.

The gyroscope flywheel 16 consists of several parts which perfrom thefollowing operation: Its axis of rotation zz remains aligned with axisyy of the fuze (and projectile) due to magnetic attraction or otherbiasing force until the launching gun is fired at which time the forcealignment is removed and divergence of the axis zz from the axis y-y ispossible; setback in the projectile, upon firing, causes separation andcounterrotation of upper and lower portions of the flywheel which keepsthe two portions apart; decay of counter-rotation below a certain valuecauses the two portions to come together, as they were prior to firing;the flywheel may provide the magnetic attraction which keeps the axesz-z and yy aligned prior to firing; and the gyroscope flywheel maintainsits attitude at firing with respect to earth during flight.

Referring to FIG. 4 along with the preceding figures, the gyroscoperheostat 17 is the portion of the outer pivot ring 14 which provides, inthe firing circuit 25, the variable resistance in conjunction with thegyroscope contact 18 and the angle of traverse y-z or movement of thecontact along the rheostat resistor 17, and means for translating thistraverse angle or movement into a useful signal by varying the firingcircuit impedance or resistance.

The adjustable rheostat 19, with its movable contact 24, is the variableresistance in the firing circuit which is selected or set at firing andin conjunction with the gyrscope rheostat 17-18, permits selectabletranslation of traverse angle y-z into angle of fall, which in turn, canbe the point of air burst. The adjustable rhesostat is calibrated inangles of traverse or other related data for setting the airburst and isselectable externally.

The arming rotor 20 provides the mechanical out-ofline safety requiredof the detonator 21 as well as safety switching therefor by means of theseries arming switch 27. Upon arming of the rotor the detonator 21 isalined with the explosive train and is connected electrically in thefiring circuit 25 by the switch 27.

The electric detonator 21 is the explosive train initiator. Safetyrequirements dictate that it will be out-of-line until the projectileleaves the launching area in order to provide the utmost safety duringmanufacture, storage, handling and firing.

It may be noted here again that the axis xx is that around which theinner pivot ring 15 rotates relative to the outer ring 14 and theresistor mounting. The 3 axis is that around which the outer pivot ring14 rotates relaitve to the housing or projectile, and it is also thelong axis of the projectile 10. Therefore it coincides with the angle ofelevation of the launching gun and the angular direction at takeoff. Theaxis zz is that around which the gyroscope flywheel 16 rotates, and theaxis R-R is that around which the rotor 20 rotates.

Referring more particularly to FIG. 4 and the firing circuit 25, theoperation is as follows: The setting rheostat 19 is adjusted to a valuewhich, in addition to that of the rheostat, equals the circuitresistance required to close the diode 13 when the energy source 12 isat the desired voltage. Then when the source 12 is charged to thedesired voltage on setback, and the resistance of the gyroscope rheostatreduces to the value which, in addition to the resistance of the settingrheostat 19 causes the diode 13 to trigger and close, the source voltagethen initiates the detonator 21 and the projectile functions.

A direct comparison between this system and those presently known andused clearly indicates that it represents a radical departure fromconventional fuzes and conventional ways of solving the problem ofreliable air-burst control. Alternative methods of construction inaccordance with the invention may include the following features:

(a) The pivots of the inner and outer pivot rings may not here be usedas conductors in the firing circuit. The pivots may be resilient totelescope or otherwise give upon setback in order to remove the loadfrom the bearings and transfer it to other members until the setbackforce subsides.

(b) Suitable magnetic aligning means may be included in the shaftportion 28 of the gyroscope flywheel or in appropriate portions of theouter pivot ring, which here is of magnetic material, to maintain theaxis z-z in line with axis y-y until the device is fired. When fired,the lower portion of the gyroscope flywheel is displaced from theinfluence of the corresponding magnets in the outer pivot ring andalinement is not maintained, permitting divergence of axis zz from axisy-y. In the present system the inner ring 15 is nonmagnetic.

(c) Movement of the axis zz with respect to the axis yy or the operatingangle y-z and rheostatic control can be geared to magnify the excursionand thereby make it more accurate. Thus, the length, and therefore theaccuracy, of the rheostat 17 may be increased as required.

(d) The gyroscope flywheel 16 can be made of two portions-the upperwhich is fixed to gyroscope shaft 28 and the lower which is separatefrom both the upper portion and the shaft. Rotation of the lower portioncan be stopped by transferring its rotative energy to the projectilebody by momentary engagement therewith. (e) The setting of theadjustable rheostat is translated into distance along the trajectory,angle of traverse, time, or other useful or suitable units of measure.The contact 18 is shown as a wiper-type, but it can be a wheel, brush orother suitable element.

The rotor 20 is shown in simple cylindrical form for the reason thatdelayed arming and self-sterilization features with a cylindrical typerotor are known and used in projectiles of this type. The axis ofrotation may be parallel with, instead of perpendicular to, the axisy-y. The rotor element is thus shown only by way of example along withthe remainder of the initiating train. Any suitable driving means may beused with the electric detonator 21 on the present fuze system. Also itwill be seen that because there is only an electric circuit connectingthe adjustable rheostat 19 with other parts of the circuit, the lattermay be hermetically sealed for long shelf life.

The operation of the airburst fuze system is as follows: Setback forcescause counter-rotation of the upper and lower portions of the gyroscopeand the arming means 20. Rotation of the flywheel fixes the position ofaxis z-z with respect to earth. Thus, in the launching means the axes yyand zz coincide. After launching and in flight as the projectileproceeds along its trajectory, the axis y-y will diverge from the axiszz and the resistance of the element 17 will decrease. The y-y and zzaxes diverge because, athough the gyroscope maintains the axis zz infixed relationship to the earth, the axis y-y does not maintain a fixedrelationship with respect to earth but, instead, follows the trajectoryof the projectile, thereby causing the axis zz to diverge from the axisy-y. This divergence is the traverse angle yz. When the resistance ofthe control element 17 is reduced to a certain value in conjunction withthe resistance of the element, it causes suflicient voltage drop acrossthe diode 3 to trigger and close it.

When the diode 13 closes it initiates the detonator 21 and functions theprojectile. Adjusting the resistor 19 to different values causes thefunctioning of the projectile at different points and effectivelyprovides selectable airburst along the trajectory which can becalibrated in suitable units as hereinbefore pointed out.

From the foregoing description, it will be seen that, with the system ofthe present invention, air-burst can be provided with accuracy at setpoints along the trajectory reliably and at relatively low cost. Thefuze system is adapted to be housed in the forward end or nose of aconventional form of explosive projectile or the like. The latter maytravel for any period or distance before the selected traverse angleoccurs. No clock work timing means is required and the number ofcomponents used is reduced effectively to a minimum. The system cannotbe actuated, that is defeated by counter-measure signals or othercounter-measure means, as a radio-signal controlled fuze system can beactuated, it does not require the use of pyrotechnic or other lightgenerating means, and is adapted for hermetic sealing for long stand-byuse or storage.

I claim:

1. An air burst fuze system for the functioning of an explosiveprojectile in flight along a curved trajectory in accordance with aselected pitch or angular position therein, comprising in combination, ahousing therefor, an electric detonator movable from a safe to an armedposition in response to movement of said projectile into flight, anarming switch connected with said detonator to be moved therewith froman open unarmed position to the closed armed position, a firing circuitfor the detonator connected or to be energized through said switch andincluding a series triggering diode device effective to conduct firingcurrent to said detonator at a predetermined higher triggering voltageapplied thereto, series variable resistance means of annular ring formconnected in circuit with said diode device to control and set theinitial voltage level applied thereto, and gyroscopic control meanshaving a fixed axis of rotation in the plane of the trajectory connectedin coaxial relation with said resistance means to effect variationsthereof and an increase in said applied voltage to the triggering levelin response to movement of the projectile in flight through saidselected pitch and angular position along said tra jectory, thereby toinitiate the functioning of said projectile.

2. An air-burst fuze system as defined in claim 1, wherein thegyroscopic control means includes inner and outer mounting ringsrelatively movable on pivot axes carrying relatively movable elements ofthe variable resistance means, and wherein the outer ring is adapted tobe connected with the housing and the inner ring is fixed with respectto the said fixed axis of rotation of the gyroscope control means.

3. An air-burst fuze system for an explosive projectile in flight in acurved trajectory over a terrain area with changing pitch or flightangle comprising in combination, an electric detonator for initiatingthe explosive action of said projectile, means providing a source ofelectric energy having a voltage output effective to fire saiddetonator, a firing circuit for said detonator connected between saidenergy source and the detonator, said circuit including a triggeringdiode device together with an arming switch and a variable resistordevice in series relation, means for closing said arming switch andmoving said detonator from a safe to an operative position in responseto setback action of said projectile, a gyroscope flywheel mounted torotate in a plane transverse with respect to the spin axis of saidprojectile, pivotal mounting means for said flywheel comprising an outerpivot ring element having a pivot axis adapted to be fixed in andcarried by said projectile in co-axial relation with the spin axisthereof and an inner pivot ring element mounted within the outer pivotring element on a pivot axis at a right angle to and in the plane of thepivot axis thereof for relative rotation in response to change in pitchof the projectile in flight to maintain the gyroscope flywheelindependent thereof and in a fixed initial attitude with respect to theterrain and the initial flight direction, means connected with saidresistor device to vary the resistance of the firing circuitcorresponding to relative movement of the said inner and outer ringelements with changes in pitch of said projectile in flight thereby tovary the effective voltage applied to the triggering diode device and toapply firing energy to the detonator therethrough with increased voltageto the break down point thereof corresponding to a desired point on thetrajectory.

References Cited UNITED STATES PATENTS 2,986,109 5/1961 Kittleman et a1.114-23 FOREIGN PATENTS 305,620 6/ 1920 Germany.

VERLIN R. PENDEGRASS, Primary Examiner.

